1. Field of Invention
The present invention relates to an arrangement of through vias (or through holes) of a wiring board, and particularly to an arrangement of non-signal through vias and a wiring board applying the same.
2. Description of the Related Art
A conventional wiring board for carrying and electrically connecting a plurality of electronic components is usually formed by a plurality of patterned conductive layers and a plurality of insulation layers disposed in an alternately overlapping manner. Each of the patterned conductive layers is made of a copper foil and defined by lithography and etching processes, and the insulation layers are disposed between two adjacent patterned conductive layers, respectively, for isolating the patterned conductive layers. The patterned conductive layers which alternately overlapped with each other are electrically connected to each other through conductive vias or conductive through vias (or “through vias” for simplicity). In addition, various electronic components (such as active components or passive components) can also be disposed on the surface of the wiring board, and internal circuits in the wiring board are used to achieve the object of electrical signal propagation.
Referring to FIG. 1, it is a cross-sectional view of a conventional wiring board. A conventional wiring board 100 includes a plurality of insulation layers 110, a plurality of patterned conductive layers 120, a plurality of through vias 130, a plurality of conductive vias 140 and a plurality of contact pads 150. One of the insulation layers 110 is a core layer 110(a). The through vias 130 include signal through vias, power through vias and ground through vias. The through vias 130 also pass through the core layer 110(a) and electrically connect some of the contact pads 150. Each of the conductive vias 140 passes through at least one of the insulation layers 110 except for the core layer 110(a). The patterned conductive layers 120 and the insulation layers 110 are alternately disposed with each other, and at least two of the patterned conductive layers 120 are electrically connected to each other through the through vias 130 and at least one of the conductive vias 140.
The disposition manner and the disposition quantity of the power through vias (or the ground through vias) among the through vias 130 are determined by the design requirement and the current carrying ability of the circuit between the power through vias (or the ground through vias) and the corresponding contact pads 150 electrically connected thereto. However, a certain number of the power through vias (or the ground through vias) among the through vias 130 in a conventional wiring board 100 are usually adjacent to each other and aggregated in the core layer 110(a) based on a circuit design consideration. Thus, for the conventional wiring board 100 to transmit current by means of the power through vias (or the ground through vias), a significant parasitic inductance would be produced. This results in a serious noise interference during switching currents.